/Engine/Source/Runtime/UMG/Public/Blueprint/WidgetTree.h
Searches recursively through the children of the given ParentWidget to find a child widget of the given name. If successful, also gets the index the child ultimately occupies within the starting ParentWidget (INDEX_NONE otherwise)
static [UWidget](API\Runtime\UMG\Components\UWidget) * FindWidgetChild ( [UPanelWidget](API\Runtime\UMG\Components\UPanelWidget) * ParentWidget, [FName](API\Runtime\Core\UObject\FName) ChildWidgetName, int32 & OutChildIndex )